The inventor has previously developed an oven which is suitable for use in baking cookies and which employs a chain conveyor for transporting product support trays from an upper to a lower level of the oven. The conveyor follows a generally serpentine path which includes a succession of horizontal passes in moving from the upper to the lower level and, during each of the horizontal passes, food items carried by the trays are exposed to overhead heating elements. Also, the trays are mounted to the conveyor in close-spaced relationship so that they tend to baffle heat migration between various notionally separate heating zones within the oven.
The above described (prior art) oven is disclosed in U.S. Pat. No. 4,004,129, granted to K. J. Hicks.
Whilst the previously developed oven has proved to be highly successful when used for baking cookies, it has not been found to be entirely suitable for baking bread. Thus, whereas cookies mixes should be exposed to relatively high initial heat from overhead heating elements when the products are first conveyed into the oven, bread dough and certain other product mixes should be subjected to deep heating. This means that the products should be exposed to heat from the underside of the product retainers during the initial baking stage and that top heat should be applied to the products only after baking has progressed beyond the initial stage.
Also, it should be mentioned that bread making involves a multi-stage process in which dough is kneaded and is set aside whilst fermentation occurs. Thereafter, the dough is punched-down, shaped, subjected to a further fermentation or "proving" period and baked. The successive proving and baking stages are subject to independent variables and it is believed that, for this reason, continuous line processing has not previously been feasible. Thus, in the baking of bread, one batch of dough may need to be subjected to a longer proving period than a second batch and, to compound the problem, it is possible that the first batch of dough may require a shorter baking period than the second batch. Therefore, it has not been possible to convey successive batches of dough serially through a proving chamber and an oven chamber because any required change in the speed of conveyance of the dough through the proving chamber would result in an unwanted corresponding change in speed of conveyance of the dough through the baking chamber. Conversely, any change made in the speed of conveyance of one batch of dough through the oven chamber would affect the speed of conveyance of a following batch of dough through the proving chamber, with potentially adverse consequencies.
Because of the need for independently variable conveyance speeds through the proving and baking chambers, such chambers conventionally are constructed as separate units and dough is loaded into the baking chamber after it has been passed through a proving chamber where it is subjected to a warm humid atmosphere. However, with the growth of point-of-sale baking businesses and the space/manpower restrictions to which such businesses are frequently subjected, a need has been created for a processing apparatus in which proving and baking may be performed serially and without a necessity for manhandling the dough from one chamber to another.